A variety of herbaceous, deciduous and conifer plants are known to possess the genetic and enzymatic capability for the synthesis and release of short-chain isoprenoids (e.g., isoprene (C5H8) and methyl-butenol (C5H10O1)) into the surrounding environment. Such short-chain isoprenoids are derived from the early Calvin-cycle products of photosynthesis, and can be synthesized in the chloroplast of herbaceous, deciduous and conifer plants via the so-called DXP-MEP pathway at substantial rates under certain environmental stress conditions. Heat-stress of the organism is particularly important for the induction of this process in plants, and the resulting hydrocarbon pollution of the atmosphere has been the focus of the prior art in this field.
Emission of isoprene from herbaceous, deciduous, and conifer plants is due to the presence of an isoprene synthase (IspS) gene, a nuclear gene encoding for a chloroplast-localized protein that catalyzes the conversion of dimethylallyl diphosphate (DMAPP) to isoprene. As noted above, isoprenoids are synthesized in the chloroplast from the early products of the Calvin cycle (carbon fixation and reduction, see FIG. 1). 5-carbon isoprenoids, e.g. isoprene (C5H8) and methyl-butenol (C5H10O1) are relatively small hydrophobic molecules, synthesized directly from DMAPP (FIG. 2). These isoprenoids are volatile molecules that easily go through cellular membranes and thereby are emitted from the leaves into the atmosphere. The process of heat stress-induction and emission of short-chain hydrocarbons by plants has been discussed as undesirable pollution of the atmosphere in the literature. There has been no description of the mass-generation, harvesting and sequestration of these hydrocarbons from the leaves of herbaceous, deciduous and conifer plants.
There is an urgent need for the development of renewable biofuels that will help meet global demands for energy but without contributing to climate change. The current invention addresses this need by providing methods and compositions to generate volatile short-chain hydrocarbons that are derived entirely from sunlight, carbon dioxide (CO2) and water (H2O). These hydrocarbons can serve as biofuel or feedstock in the synthetic chemistry industry.